Unit VIII - Ear Pt. 2 Flashcards
What SURROUNDS the membranous labyrinth?
Perilymph within the bony labyrinth
What is another name for the inner ear?
Labyrinth
What are the parts of the bony labyrinth?
Cochlea, vestibule, semicircular canals
What is the shape of the cochlea, and what does it contain?
Snail shell shaped; contains cochlear duct
What is contained in the vestibule?
Utricle and saccule
What do the lateral, anterior, and posterior semicircular canals contain?
Semicircular ducts
What fluid is located WITHIN the membranous labyrinth?
Endolymph
The utricosaccular duct is located between what two structures?
Utricle and saccule
What structures are found in the vestibular labyrinth?
Utricle, saccule, semicircular ducts, utricosaccular duct, endolymphatic duct and sac, ductus reuniens
What is the cone-shaped central bony structure that the cochlea wraps around 2.5 to 2.75 times?
Modiolus
What is the name of the apex of the cochlea?
Cochlear cupula
The cochlear cupula lies in what direction?
Anterolaterally
What is the bony ridge that connects the cochlea to the modiolus?
Lamina of the modiolus
What three channels make up the cochlea?
Cochlear duct, scala vestibuli, scala tympani
Where does the cochlear duct end?
Apex of cochlea
How do the scala vestibuli and scala tympani communicate?
At the apex through a channel called the helicotrema
What fluid fills the scala vestibuli?
Perilymph
As the stapes vibrates, where are the vibrations transmitted?
Into the scala vestibuli
Which structure is located above the cochlear duct: scala vestibuli or scala tympani?
Scala vestibuli
Which structure is located below the cochlear duct: scala vestibuli or scala tympani?
Scala tympani
How do vibrations that are transmitted through the scala vestibuli pass to the scala typani?
Via the helicotrema
What is the base of the scala tympani?
Round window
What forms the base of the scala vestibuli?
Oval window
Where is the cochlear duct located and what is found above and below it?
Middle of the bony labyrinth with scala vestibuli above and scala tympani below
What fills the cochlear duct?
Endolymph
The cochlear duct is attached to what structure?
Lamina of the modiolus
What anchors the cochlear duct to the outer wall of the cochlea?
Spiral ligament
What separates the cochlear duct from the scala vestibuli?
Vestibular membrane
What separates the cochlear duct from the scala tympani?
Basilar/spiral membrane
Where is the spiral organ located, and what is it attached to?
On the floor of the cochlear duct; attached to basilar/spiral membrane
What is the purpose of the numerous hair-like projections that project superiorward from the basilar/spiral membrane of the spiral organ?
They are sensitive to frequency and amplitude of sound waves that enter the cochlea
What covers the hair cells seen in the spiral organ?
Tectorial membrane
Where are the cell bodies located for the primary sensory neurons of the spiral organ that receive information from the receptor cells?
Spiral ganglion
When sound waves enter the external acoustic meatus, what structure vibrates?
Tympanic membrane
What structures transmit the vibrations from the tympanic membrane?
Ossicles of the middle ear (malleus, incus, and stapes, in that order)
What process amplifies the vibrations 1.2 times?
Transmission of vibrations through middle ear ossicles
What is the reason that vibrations that enter the external acoustic meatus are amplified another 17 times?
The oval window diameter is much smaller than the tympanic membrane
The foot of which ossicle articulates with the oval window?
Stapes
What forms the base of the scala vestibuli?
Oval window
After the vibrations are transmitted through the ossicles, where are they then transmitted?
Through the perilymph of the scala vestibuli and the scala tympani, eventually reaching the round window
After the vibrations are transmitted through the perilymph, what structure vibrates, and what is the result?
Basilar membrane; stimulation of receptors in the spiral organ
After the receptors in the spiral organ are stimulated, where is the information then transmitted?
To the cochlear nerve
What fluid is contained in the saccule, utricle, and three semicircular ducts?
Endolymph
What are the three semicircular ducts?
Anterior, lateral, posterior
What does the saccule communicate with?
Cochlear duct
Which is larger: saccule or utricle?
Utricle
What does the utricle communicate with?
All three semicircular ducts and the saccule
How does the utricle communicate with the saccule?
Utricosaccular duct
What are the sense organs within the utricle and saccule?
Hairlike projections called maculae
What bathes the maculae?
Endolymph
What tiny structures float on the endolymph that bathes the maculae?
Otoliths
What kind of action causes the otoliths to deflect the maculae and thus elicit impulses?
Movements of the head
Which detects centrifugal and linear in any direction accelerations: utricle or saccule?
Utricle
Which detects linear accelerations: utricle or saccule?
Saccule
What are the sense organs located within the semicircular ducts?
Crista
Where are the crista located in the semicircular ducts?
In the ampulla of each duct
What movements are the semicircular ducts sensitive to?
Accelerations in any direction, but particularly sensitive to rotational accelerations
Where are the cell bodies located for the neurons that carry information from the impulses that are initiated by the sense organs of the vestibular labyrinth (maculae and crista)?
Vestibular ganglion
What are the two branches in which the dendrites carrying information to the vestibular ganglion are collected in?
Superior and inferior branch
Which branch carrying information to the vestibular ganglion is larger?
Superior branch
Which branch to the vestibular ganglion carries information from the anterior and lateral semicircular ducts, utricle, and some from the saccule?
Superior branch
Through what nerve is information carried from the saccule to the superior branch?
Voit’s nerve
The inferior branch to the vestibular ganglion carries information from where?
Posterior semicircular duct and saccule
What nerve is made up of axons from the vestibular ganglion?
Vestibular nerve
What makes up the blood supply to the labyrinth?
Internal auditor artery, a branch from the basilar artery
Stylomastoid artery, a branch from the posterior auricular artery
What makes up the nerve supply to the labyrinth?
Sympathetics from cavernous and/or internal carotid plexuses
Cochlear nerve
Vestibular nerve
The cochlear nerve is composed of axons of cells from where?
Spiral ganglion
What is the pathway of information through the cochlear nerve?
Cochlear nuclei –> superior olivary and trapezoid nuclei in medulla oblongata –> lateral lemniscus –> inferior colliculi and medial geniculate bodies –> temporal lobe (Bdmn. areas 41 and 42)
The vestibular nerve is composed of axons from where?
Vestibular ganglion
What is the pathway of information through the vestibular nerve?
Vestibular nuclear complex of medulla oblongata –> processed in cerebellum
